1. Field of the Invention
This invention generally relates to circuit interrupter apparatus and, more particularly, to an improved arc chute assembly for a circuit breaker of the low voltage type.
2. Description of the Prior Art
It is common practice in the low voltage circuit breaker art to employ an arc chute assembly to extinguish the arc that is produced when the circuit breaker is tripped and the contacts are rapidly opened. Such arc chute assemblies consist of a plurality of metallic chute plates that are held in stacked spaced-apart relationship by side panels and a back panel that are fabricated from electrically non-conductiuve material. Retention of the chute plates in assembled relationship was usually achieved by providing them with small tabs which were slipped into a series of openings in the side panels and then staked or spun over at final assembly. Such staking and spinning operations were not only expensive and time consuming but frequently damaged the protective finish or plating that is provided on the arc chute plates to prevent rusting and enhance their arc-extinguishing ability. An arc chute assembly having staked arc chute plates that are coated with a weld deterrent material such as silicone varnish is disclosed in U.S. Pat. No. 4,143,256 (Ciarcia).
An improved arc chute assembly having arc plates that are provided with notched tangs which interfit with slots in the insulative side panels and are locked in place by an insulative back panel which engages apertures in the side panels in snap-fitting relationship is disclosed in U.S. Pat. No. 4,107,497 issued Aug. 15, 1978 to Jencks et al.
Various other types of arc chute assemblies and means for keeping the components in stacked operative relationship are disclosed in the following U.S. Pat. Nos. 2,551,822 (Bingenheimer et al.), 2,911,505 (Legg et al.), 3,243,559 (Heft), 3,749,867 (Rexroad) and 4,229,630 (Wafer et al.).
While the prior art arc chute assemblies were satisfactory from a functional standpoint they were difficult and expensive to manufacture in that they required staking or spinning of arc plate material to lock the plates in place or a temporary deformation of the chute components to effect a snap fit with the back panel and thus hold the assembly in the desired form. It would accordingly be advantageous from both a cost and manufacturing standpoint if such staking, spinning and snapfitting operations could be entirely eliminated during fabrication of arc chute assemblies designed for use in circuit breakers and similar apparatus.